Regular Article

Development of process for reduction in fines generation at direct reduced iron plant by coating of magnetite iron ore fines on hematite iron ore pellets

JSW Steel Limited, Bellary, India

^* e-mail: uma.devi@jsw.in

Received: 25 April 2022
Accepted: 22 September 2022

Abstract

Iron ore pellet fines generation at direct reduced iron (DRI) plant is ranging from 10 to 12% during handling of the pellets from pellet plant to DRI plant. The generation of fines during handling depends on the quality of the produced pellets, mainly due to the abrasion index (AI) of the pellet. To reduce the generation of pellet fines, detailed laboratory studies have been carried out by coating the hematite iron ore pellet surface with magnetite fines generated from reduction roasting plant, and mixed magnetite fines with limestone fines. The coated green pellets were fired in a rising hearth furnace. The magnetite fines were varied from 0 to 2.5% as coating agent, and limestone fines was varied from 0 to 0.6% as coating agent mixed with magnetite fines. At optimum 1.5% magnetite fines as coating agent achieved better pellet properties and reduced the fines generation from 6.8 to 3.2% due to formation of secondary hematite phases at the pellet shell. With mixed 0.2% limestone and 1.5% magnetite fines reduced pellet fines generation from 6.8 to 4.2%. Reduction in fines generation with mixed fines was due to formation of secondary hematite and Ca-ferrite at the pellet surface. Secondary hematite and Ca ferrite phases having higher micro-hardness compared to other phases of iron ore pellet. The sequence of micro-hardness of the pellet phases is secondary hematite > Ca-ferrite > primary hematite > magnetite. The secondary hematite and Ca-ferrite formed at the pellet surface due to coating of magnetite as well as magnetite with limestone fines improved the overall pellet quality and reduced the generation of fines at DRI plant. Coating of magnetite fines alone showed better pellet properties with lesser fines generation compared to coating of mixed limestone and magnetite fines.