Development of Firing Schedule to Prepare Composite Pre-reduced (CPR) Pellets.

Abstract

The newly developed CPR (composite pre-reduced) pellet, consists of a metallised sponge iron core encased in a partially reduced and sintered iron oxide shell. Such CPR pellets are obtained by firing a composite iron ore-coal char pellet prepared by two stage pelletisation. Iron ore and coal char mixed in desired proportion are pelletised to form core pellet which is further coated with iron ore only during second stage pelletisation. Such CPR pellets being developed mainly to utilise plant waste for preparing a cheap metallised feed for use in blast furnace. When composite iron ore-coal pellets are fired in air, CO(g) generated in core reduces not only iron oxide in-situ but also the outer shell partially. The continued firing reoxidised the reduced pellet unwillingly. The present paper gives a basic study of firing time and temperature to study the reduction behaviour of composite pellets followed by microstructural examination of fired and reduced pellets. The firing schedule, thus, developed was tested to prepare bulk quantity of CPR pellets having 28.6% metallic iron, out of total 76.6% Fe in the pellet rendering nearly 48% overall reduction degree together with sufficient strength (120±20 kg) which may enable its use as blast furnace feed.