2003 Volume 43 Issue 1 Pages 20-25
This paper involves the preparation technologies of cold bonded pellets for direct reduction using an organic binder-Funa. Investigation shows that the binder possesses excellent adhesive abilities to iron ore concentrates and is the key to the preparation of cold bonded pellets. Pretreatment on the binder-bearing iron concentrates prior to balling operation is essential to the maximization of adhesion of the binder to ore particles. Roll drum milling was found to be an effective method for the purpose. Investigation also shows that iron ore concentrate containing the organic binder has a lower balling kinetics than bentonite concentrate due to the increased viscosity by the binder. A balling time of 20 min is needed to ensure the pellet strength. It is found that the appropriate drying and hardening conditions for wet balls are 200-250°C of temperature and 0.8-1.0 m/s of airflow rate. TGA and DTA detection shows that the organic binder is thermally stable below 250°C in either neutral or oxidative atmosphere. Under above conditions, cold bonded pellets with a compressive strength of 250-300 N/Pellet, a drop strength of 7-10 times/1.0 m and a resistance to abrasion over 98% (+3 mm) have been attained from magnetite concentrates by using 1.5% of the organic binder. Tests show that the cold bonded pellets present a greater reduction rate and a higher iron grade of products than fired pellets made with bentonite as binder.