Engineering Chemistry S Datta

METALLURGY 311
(v) Magnesium Epsomite (MgSO 4
.7H 2
O)
Kisserite (MgSO 4
.H 2
O)
(i) Sodium
(ii) Potassium
(iii) Silver IB (Conductive metal)
Rocksalt (NaCl)
Sylvine (KCl)
Horn silver (AgCl)
Halides (iv) Calcium Fluoropalite (3CaF 2
Ca 3
(PO 4
) 2
); Chloropative
(v) Magnesium
(3COCl 2
.Ca 3
(PO 4
) 2
)
Carnallite KCl, MgCl 2
6H 2
O
(vi) Aluminium Cryolite (3NaF, AlF 3
)
(i) Sodium Sodium silicate (Na 2
SiO 3
)
(ii) Potassium Felspar (K 2
O.Al 2
O 3
.6SiO 2
)
Silicates (iii) Zinc Willemite (ZnSiO 2
)
Ores
(iv) Aluminium Felspar (K 2
O.Al 2
O 3
.6SiO 2
)
Generally all minerals cannot be considered important for extraction of metal from them.
The process of extraction though costly may not be impossible from these minerals.
Particularly, the minerals from which metals can be extracted easily and cheaply
are known as ores. As for example, haematite is the ore of iron, bauxite is the ore for aluminium
etc.
Metallurgy
The process by which the metals are extracted from their respective ores is
known as metallurgy. An ore is naturally occurring substance or mineral from which the
metal can be extracted economically.
Concentration of the Ore
Almost all ores are associated with gangue or matrix. Before the proper extraction of the
metal the ore is freed from gangue or matrix to get it in the concentrated form. As a matter of
fact, the ore is enriched with the desired metallic compound. This process of removal of gangue
is known as the concentration of the ore. There are several processes of the concentration of
ores, which are described below. This process of concentration of ore makes the extraction of the
metal easier and cheaper. The main steps for the extraction of metals are generally as follows:
1. Crushing and grinding
2. Concentration of the ore
3. Calcination/Roasting
4. Reduction
5. Purification
Crushing and Grinding. This is one of the crucial steps of concentration process. The
step provides breaking of big masses of rocks containing the ore into small lumps by conventional
crushing and grinding with machines viz., Jaw crusher, Gyratory crusher etc.
Sometimes, the concentration and further treatment of some ores demand their reduction
of size into a very fine state of division. This is effected in grinding and pulverising mills
(Figs. 14.2 and 14.3).