# Roasting of iron ore

> Heating in air: drier ore, more iron, fewer impurities


## Objectives

- State the meaning of roasting and its two purposes in the book's words.
- Write the roasting equations of siderite, FeO, limonite, sulphur and phosphorus.
- Explain why roasting raises the iron percentage of the ore.
- Recognize that roasting oxidizes impurities and does not reduce the ore.

## 1. Iron ores and extraction of iron




## 2. More iron, with no iron added?

Predict: where does the higher percentage come from?

- Gases leave the solid, and the iron stays ✓
- Heating reduces the ore to iron metal
- Heating makes new iron atoms

Heating in air cannot create iron atoms and does not reduce the ore. Gases ($\ce{CO2}$, water vapour) leave the solid, so the same iron mass sits in a smaller total mass and its percentage rises.

[ar-EG] التسخين في الهوا مايقدرش يخلق ذرات iron ومش بيعمل reduction للـ ore. الغازات ($\ce{CO2}$ وبخار الميّة) بتخرج من المادة الصلبة، فنفس كتلة الـ iron بتبقى في كتلة كلية أصغر ونسبته بتزيد.
## 3. What roasting is

Roasting The ore is strongly heated in air. Ore dressing: improving the physical, then the chemical properties of the ore Roasting improves the chemical properties of the ore. It is part of ore dressing, before reduction.


## 4. Purpose 1: more iron in the ore

Purpose (a): drying the ore and expelling humidity, to increase the percentage of iron in the ore. Equation Siderite decomposes Thermal decomposition: $\ce{CO2}$ gas leaves the solid. FeO is oxidized Siderite overall: 48% Fe → about 70% Fe (the book prints 69.6%) FeO gains oxygen from the air: oxidation. On its own, this step lowers % Fe (FeO about 78% → $\ce{Fe2O3}$ about 70%). The rise is counted on siderite overall: $\ce{FeCO3}$ (48% Fe) → $\ce{Fe2O3}$ (about 70% Fe). Limonite loses its water The water of crystallization leaves as vapour.


## 5. Why the iron percentage rises

Follow 2 mol of pure $\ce{FeCO3}$ all the way to $\ce{Fe2O3}$ (Fe = 56, C = 12, O = 16). Rounded atomic masses. The book's labels: 48.5% (FeCO₃) and 69.6% (Fe₂O₃). The iron mass does not change. The total mass falls, so iron's share rises.


## 6. Purpose 2: oxidizing impurities

Purpose (b): oxidation of some impurities such as sulphur and phosphorus. Roasting melts sulphur and phosphorus out of the ore. Balance the phosphorus equation.


## 7. Decomposition or oxidation?

Sort each roasting reaction by what happens to it. Sort the reactions. Roasting reduces the ore.


## 8. Check yourself

Limonite, $\ce{2Fe2O3*3H2O}$, is roasted. Why does the iron percentage of the solid rise?

- The heat reduces $\ce{Fe2O3}$ to iron.
- Water vapour leaves; the iron stays in less total mass. ✓
- Iron from the furnace walls joins the ore.
- Oxygen from the air turns into iron.

On roasting, limonite loses its water of crystallization as vapour: $\ce{2Fe2O3*3H2O -> 2Fe2O3 + 3H2O}$. The iron mass stays the same in a smaller total mass, so the iron percentage of the solid rises.

[ar-EG] في الـ roasting الـ limonite بيخسر الـ water of crystallization بتاعه على شكل بخار: $\ce{2Fe2O3*3H2O -> 2Fe2O3 + 3H2O}$. كتلة الـ iron بتفضل زي ما هي في كتلة كلية أصغر، فنسبة الـ iron في المادة الصلبة بتزيد.
## 9. Summary

Siderite in roasting: gases leave, oxygen is added, iron stays Roasting: the ore is strongly heated in air. (a) Drying the ore and expelling humidity, to increase the percentage of iron. (b) Oxidation of some impurities such as sulphur and phosphorus. Iron stays; gases ($\ce{CO2}$, water vapour) leave. The ore is not reduced here. Give reasons: the iron percentage rises on roasting. Key words: moisture and gases expelled; iron mass stays; total mass decreases. Back to the hook: can you explain how siderite becomes richer in iron without any iron added?



Chapter: Transition Elements (https://yaani.ai/en/learn/chemistry/chem-s3-en.ch1)
Source: https://yaani.ai/en/lesson/chem-s3-en.lesson-fe.roasting