Use of Iron Ore Fines in Cold-Bonded Self-Reducing Composite Pellets

ABSTRACT

The feasibility of producing direct reduced iron from cold-bonded, self-reducing composite pellets, constituted from beneficiated iron ore slime, coke, and different binders (dextrin, bentonite, calcium lignosulfonate, and carboxymethyl-cellulose [CMC]) was studied. This was done using a design of experiments approach. It was found that as-received beneficiated iron ore slime is suitable as a raw material for the production of self-reducing composite pellets with carboxymethylcellulose as the most suitable binder. Dry strengths in excess of 300 N/pellet were attained by curing the pellets under ambient conditions. The composite pellets reduced within 20 min to degrees of metallization in excess of 90% at 1100°C, with decrepitation indices significantly below 5%. The degree of metallization of composite pellets increased with an increase in reduction temperature (from 1000 to 1100°C), reduction time (20 min. vs. 40 min), and coke quantity (15% vs. 20%). CMC was identified as the most economical and suitable binder for the Sishen concentrate.

KEYWORDS:

• Beneficiated iron ore slime
• cold-bonding
• direct reduced iron
• organic binder
• self-reducing composite pellets

Acknowledgments

The authors would like to express their gratitude to Anglo American Kumba Iron Ore Value-in-Use for providing raw materials, use of equipment, and technical support.

Additional information

Funding

The authors would like to thank Anglo American Kumba Iron Ore and the National Research Foundation of South Africa (Grant number TP2009072800103) for sponsoring this study.