Engineering Chemistry S Datta

314 ENGINEERING CHEMISTRY
Selection of Flux
The nature of flux to be used depends on the nature of gangue. If it is acidic, basic flux is
to be used viz. lime, magnesia etc. If the gangue is basic in character, then an acid flux like sand
(SiO 2
) must be employed.
There are three kinds of fluxes:
• Acidic (SiO 2
)
• Basic (CaO, MgO)
• Neutral (fluorspar)
Fuels
Almost all industries require a fuel. Large scale industries, like metal extraction, need
economy of fuel consumption.
Furnaces
• Reverberatory furnace. This is a special type of furnace much used in metallurgy. In
this furnace, the material is heated not directly over fire, but by the hot gases produced
in the fire place (Fig. 14.6).
Chimney
Charge
(Hopper)
Hearth
Ore
Flame fuel
Air
Fig. 14.6 Reverberatory furnace.
• Muffle furnace. It is a type of furnace consisting of an enclosed chamber, made of
refractory materials, from which the fuel and its products of combustion cannot come
in contact with the materials heated in it (Fig. 14.7).
Fig. 14.7 Muffle furnace.
• The other furnaces are blast furnace (for iron extraction), open hearth furnace (for
steel manufacture) and electric furnace (for Phosphorus extraction).