Effects of bentonite fiber formation in iron ore pelletization

In the production of iron ore concentrate pellets, binders are required to improve pellet green strength. The most popular binder for this purpose is bentonite clay, which is added at a rate of approximately 0.5–1.0% by weight of moist concentrate. Bentonite is a significant cost item in iron ore pelletization, and also contributes undesirable amounts of silica to the finished pellets. If the binding effectiveness of bentonite is increased, it will be possible to reduce the bentonite dosage, resulting in significant cost savings while producing higher quality, lower silica pellets. The authors have recently identified a new and important bentonite binding mechanism, which is development of bentonite fibers under compressive shear mixing. During this study, procedures were developed that took advantage of the ability of bentonite to form fibers, and resulted in a dramatic decrease in the necessary bentonite dosage. When mixing procedures were used that promoted fiber formation, the bentonite dosage needed to produce acceptable strength pellets was cut in half, from 14 (0.66%) to 7 (0.33%) lb/lt. In addition, bentonites that are currently considered poor quality can have their performance enhanced by using this fiber development method, and be used successfully as iron ore pellet binders.