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Lesson 3 Iron Ore Extraction, Reduction Furnaces and Alloy Classifications
├── Occurrence
├── Important ores
├── Steps of extraction
├── Alloys
├── Preparation of alloys
├── Types of alloys
└── Some alloys and their uses

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Occurrence

Iron is the fourth most abundant element in the Earth’s crust (after O, Si, Al), about 5 % by mass, and its proportion increases towards the Earth’s core.
Free metallic iron (about 90 % pure) occurs only in meteorites; otherwise it is found as ores — natural iron oxides mixed with impurities.
A good ore is judged by (1) the percentage of iron, (2) the nature of the impurities (gangue), (3) harmful elements such as sulphur, phosphorus and arsenic.

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Important ores

Ore	Formula	Properties	Fe %	Place in Egypt
Hematite	Fe₂O₃ (iron(III) oxide)	blood-red; reduced easily	50–66	Oases (Western Desert)
Limonite	2Fe₂O₃·3H₂O (hydrated oxide)	yellow; easily reduced	20–60	Oases area
Magnetite	Fe₃O₄ (magnetic oxide)	black, magnetic	45–70	Eastern Desert
Siderite	FeCO₃ (iron(II) carbonate)	yellowish-grey; easily reduced	about 30–42	Oases area

Worked example 4 (iron content of a pure ore).→Using Fe = 56, O = 16, C = 12:

Comparison aspect	Main idea	Keywords
Fe₂O₃ (M = 160)	%Fe = 112/160 × 100 = 70 %
Fe₃O₄ (M = 232)	%Fe = 168/232 × 100 = 72.4 %
FeCO₃ (M = 116)	%Fe = 56/116 × 100 = 48.3 %. After roasting to Fe₂O₃ the iron content of what remains rises to 70 % which explains why siderite is roasted before reduction. Natural ores are always lower than these figures because of the gangue	AfterroastingFe₂O₃iron

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Steps of extraction

Step 1 — Ore dressing (preparation).→It aims to:

Crushing — gives lumps of suitable size for easy reduction. Sintering — the crushing process produces large quantities of fine particles that cannot be fed directly to the furnace (they would be blown out and block the flow of gases), so they are fused together into larger, uniform lumps. Concentration — raises the percentage of iron by removing the impurities mixed with or combined in the ore, using surface tension (flotation), magnetic or electric separation. (Magnetic separation suits magnetite because it is attracted by a magnet while the gangue is not.)
Improve the chemical properties by roasting (strong heating in air) to:
a. dry the ore and expel moisture / water of hydration / CO₂, which raises the iron percentage:
- FeCO₃ → FeO + CO₂, then 4FeO + O₂ → 2Fe₂O₃ (overall 4FeCO₃ + O₂ → 2Fe₂O₃ + 4CO₂)
- 2Fe₂O₃·3H₂O → 2Fe₂O₃ + 3H₂O
  b. oxidize impurities such as sulphur and phosphorus to gases/oxides, which can be removed: S + O₂ → SO₂; 4P + 5O₂ → 2P₂O₅.

Step 2 — Reduction of the oxide to iron.Done by one of two methods, depending on the reducing agent.

(a) Blast furnace (reducing agentcarbon monoxide from coke).

Comparison aspect	Main idea	Keywords
•	The furnace is a tall steel tower lined with refractory (fire) bricks charged from the top with a mixture of roasted ore coke and limestone while a blast of hot air is forced in near the bottom	furnacetallsteeltower
Coke burns	C + O₂ → CO₂ (exothermic supplies the heat) the CO₂ reacts with hot coke higher up: CO₂ + C → 2CO	exothermicsuppliesheatreacts
Reduction (about 700 °C and above)	Fe₂O₃ + 3CO → 2Fe + 3CO₂ (taking place stepwise: Fe₂O₃ → Fe₃O₄ → FeO → Fe at progressively lower levels of the furnace as the temperature rises)	Fe₂O₃3CO₂takingplace
Limestone is added as a flux	CaCO₃ → CaO + CO₂ CaO + SiO₂ → CaSiO₃ (slag). The silica (SiO₂) of the gangue would otherwise form a refractory solid as calcium silicate it melts is less dense than molten iron floats on it and is run off separately. (Slag is used in cement making and road building.)	CaCO₃SiO₂CaSiO₃slag
•	The molten iron collects at the bottom of the furnace and is run into moulds. The product is pig (cast) iron — hard and brittle with about 4 % carbon plus S P and Si	moltenironcollectsbottom

Worked example 5 (blast furnace).→A hematite ore contains 80 % Fe₂O₃. For 1000 kg of ore (Fe = 56, O = 16, C = 12, Ca = 40, Si = 28):

Fe₂O₃ present = 800 kg. Fe₂O₃ + 3CO → 2Fe + 3CO₂: 160 kg gives 112 kg Fe, so the iron obtained = 800 × 112/160 = 560 kg (theoretical).
CO needed = 800 × (3 × 28)/160 = 420 kg = 420/28 = 15 kmol, which occupies 15 × 22.4 = 336 m³ at STP.
If the gangue contains 60 kg of SiO₂ CaO + SiO₂ → CaSiO₃ needs 60 × 56/60 = 56 kg CaO, which comes from 56 × 100/56 = 100 kg of CaCO₃; the slag formed is 60 + 56 = 116 kg CaSiO₃.
(b) Midrex process (reducing agent a mixture of CO and H₂ made from natural gas, about 93 % methane).

Comparison aspect	Main idea	Keywords
Reforming	2CH₄ + CO₂ + H₂O → 3CO + 5H₂	2CH₄
Reduction	Fe₂O₃ + 3CO → 2Fe + 3CO₂ and Fe₂O₃ + 3H₂ → 2Fe + 3H₂O	Fe₂O₃3CO₂3H₂O
•	The product is a solid porous "sponge iron" (direct-reduced iron) cleaner than blast-furnace iron because the iron never melts and no coke is used	productsolidporoussponge
Worked example 6 (Midrex).	To reduce 80 kg of Fe₂O₃ (0.5 kmol) with hydrogen: Fe₂O₃ + 3H₂ → 2Fe + 3H₂O needs 1.5 kmol H₂ = 1.5 × 22.4 = 33.6 m³ at STP and gives 1 kmol = 56 kg Fe	reduceFe₂O₃kmolhydrogen
•	Step 3 — Production of cast iron and steel	StepProductioncastiron

Steel making depends on (1) removing impurities from the furnace iron and (2) adding elements that give the steel the required properties.
It is carried out in the oxygen converter, the open-hearth furnace or the electric furnace.
In the oxygen converter a jet of pure oxygen is blown into the molten iron; carbon is oxidized to CO and silicon, phosphorus and sulphur to oxides that join the slag, and the required alloying elements are then added.

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Alloys

An alloy is a solid mixture (or compound) of two or more metals, or of a metal with a non-metal such as carbon (steel).
Examples ferrochromium, ferromanganese, ferrovanadium, ferronickel.
Alloys are used because they often have better properties than the pure metals they contain.
An alloy of iron with manganese is harder than ordinary steel, which makes it suitable for railway tracks.
An alloy of aluminium with manganese resists corrosion well, so it is used to make the containers for fizzy drinks.
Bronze, an alloy of copper and tin, is another example; it is used to make the third-place medals at the Olympic Games.

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Preparation of alloys

Comparison aspect	Main idea	Example	Keywords
Melting	the components together and cooling gradually	—	componentstogethercoolinggradually
Simultaneous electro-deposition	of two or more metals from a solution of their ions —	plating an iron handle with brass (Cu + Zn) from a solution containing copper and zinc ions	metalssolutionionsplating

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Types of alloys

Comparison aspect	Main idea	Example	Keywords
Interstitial alloys.	In a pure metal the atoms lie in closely packed layers that slip over one another when hammered (so the metal is malleable and ductile). If small atoms (	carbon) are placed in the spaces between the large atoms of the host metal the layers can no longer slide so the metal becomes harder and its malleability ductility melting point electrical conductivity and magnetic properties change. Example: steel (iron + carbon)	puremetalatomsclosely
Substitutional alloys.	Atoms of nearly equal size replace some atoms of the host metal in the lattice. Examples: ferrochrome in stainless steel copper–gold alloy ferronickel brass	—	Atomsnearlyequalsize
Inter-metallic alloys.	The elements combine chemically to form a compound whose formula does not obey the usual valency rules the metals are not from the same group. Examples: Al–Ni and Al–Cu alloys (duralumin-type alloys) Au₃Pb and cementite Fe₃C	—	elementscombinechemicallyform

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Some alloys and their uses

Alloy	Components	Use
Steel	Fe + C	construction machines tools (hardness rises with carbon content but so does brittleness)
Stainless steel	Fe + Cr (+ Ni)	cutlery surgical tools tanks that must not rust
Ferromanganese	Fe + Mn	railway tracks (harder than steel)
Vanadium steel	Fe + V	car springs
Nickel–chromium	Ni + Cr	heating coils and electric furnaces
Brass	Cu + Zn	fittings, instruments, plating
Bronze	Cu + Sn	statues, coins, bearings
Duralumin	Al + Cu (+ Ni, Mn)	aircraft parts

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Part 9

📖

🔍 In-Depth Explanations, Deductions & Multi-Book Insights:

Chemistry Thanaweya Amma (2026/2027)

Lesson 3 – Iron Ore Extraction, Reduction Furnaces and Alloy Classifications
Detailed Academic Lesson Overview:
Iron extraction involves ore dressing (crushing, sintering, concentrating, and roasting), reduction in either the Blast Furnace or Midrex Furnace, followed by steelmaking in electric or oxygen converters.

🌳 Hierarchy Classification & Conceptual Roadmap

Iron Metallurgy and Alloys

├── 1. Ore Dressing & Roasting

│ ├── Crushing & Sintering (Optimizing grain size)
│ ├── Concentration (Magnetic separation, froth flotation to eliminate gangue)
│ └── Roasting (Heating in air to dry ore, oxidize impurities like S and P, and convert to Hematite Fe₂O₃)

├── 2. Reduction Furnaces

│ ├── Blast FurnaceReducing agent is Carbon monoxide (CO) generated from Coke (C)

│ └── Midrex FurnaceReducing agent is Water Gas (CO + H2) generated from Methane (CH4)

└── 3. Alloy Classification

Comparison aspect	Main idea	Keywords
├── Interstitial Alloys	Carbon atoms fit into interstitial spaces of Iron lattice (Carbon steel)	CarbonatomsspacesIron
├── Substitutional Alloys	Atoms replace each other (Fe-Ni Fe-Cr stainless steel Cu-Au)	Atomsreplacestainlesssteel
└── Intermetallic Alloys	Chemical stoichiometric formula without IUPAC valence laws (Cementite Fe3C)	Chemicalstoichiometricformulawithout
•	📋 Master Teacher's Blackboard Rules & Exam Secrets	MasterTeacherBlackboardRules
RULE 1	Blast Furnace reducing gas is CO produced by: C + O2 → CO2 then CO2 + C → 2 CO	BlastFurnacereducingproduced
RULE 2	Midrex Furnace uses Natural Gas (93% CH4) reacted with CO2 and H2O to produce Water Gas: 2 CH4 + CO2 + H2O → 3 CO + 5 H2	MidrexFurnaceusesNatural
RULE 3	Intermetallic alloys (like Cementite Fe3C Duralumin Al-Cu or Al-Ni) do not follow ordinary valence rules and form extremely hard brittle crystal lattices	IntermetallicalloyslikeCementite
📊 Detailed Comparison Matrix	Comparative Analysis: Blast Furnace vs. Midrex Reduction Furnace	ComparativeAnalysisBlastFurnace

Feature	Blast Furnace	Midrex Furnace
Primary Ore Input	Hematite (Fe₂O₃)	Hematite (Fe₂O₃) pellets
Source of Reducing Agent	Coke fuel (Carbon, C)	Natural Gas / Methane (CH₄)
Active Reducing Agent	Carbon Monoxide (CO)	Water Gas (CO + H₂)
Primary Iron Product	Pig / Cast Iron (molten)	Sponge Iron (solid porous Fe)
Reduction Temp	Above 700°C	750°C to 800°C

Lesson 3: Iron Ore Extraction, Reduction Furnaces and Alloy Classifications · 9 / 9

Curriculum

Chemistry

Chapter 1 - Transition Elements and Iron Metallurgy

Chapter 2 - Chemical Analysis

Chapter 3 - Chemical Equilibrium

Chapter 4 - Electrochemistry

Chapter 5 - Organic Chemistry

More lessons

Lesson 3: Iron Ore Extraction, Reduction Furnaces and Alloy Classifications