General :
The major Raw Materials required for production of Sponge Iron by the rotary kiln process are: sized graded Iron Ore and Non-Coking coal. Limestone, in small quantities, is also required to scavenge the sulphur.
IRON ORE
The quality requirement of Sized ore for sponge iron production can be classified into :-
(1) Physical requirements :-
Strength and granulometry are the two important physical requirements. The ore should be hard, and posses high strength. The optimum tumbler strength of the ore should be 90 percent minimum. Depending on the reducibility, closely calibrated ores in the size range of 5 to 20 mm generally used.
(2) Metallurgical Requirements :-
The ore should be highly reducible, thermally stable and have a low tendency for sticking and disintegration during heating and reduction.
(3) Chemical Requirements :-
Apart from the removal of oxygen, no other major chemical change takes place in direct reduction. The gangue material in sponge iron, originating from Iron Ore, namely, silica and alumina and the sulphur and phosphorous contents adversely affect the economics in subsequent steel making operation. Therefore, the ore should be high in iron content and low in gangue,
COAL
Non-coking coal is used as reluctant in the rotary kiln process.
The major quality requirements of coal for Sponge iron production are :-
