Improvement of Preheated and Fired Compressive Strength of Pellets Produced with Organic Binders as a Substitute for Bentonite

Pelletizing is one of the downstream processes in ironmaking operations. Iron ore concentrate, due to its fine particle size, cannot be directly charged into reduction furnaces and therefore must be agglomerated. To ensure sufficient mechanical strength of the produced pellets during handling and firing, binders are added to the concentrate. Currently, bentonite is widely used as a pelletizing binder. However, owing to its high silica and alumina impurity content, bentonite increases slag volume and causes various operational challenges during ironmaking. As a result, considerable research efforts have been directed toward identifying suitable alternatives to bentonite. Among these alternatives, organic binders are attractive because they contain no mineral impurities and do not adversely affect the structure of iron ore concentrate. The main drawback of organic binders is their low decomposition temperature (approximately 250 °C), which causes them to burn out during preheating and firing, leading to a reduction in the compressive strength of fired pellets. Previous studies have shown that this limitation can be overcome by modifying the structure of organic binders. In the present study, the properties of pellets produced using bentonite, carboxymethyl cellulose (CMC), sodium lignosulfonate, and VETA OB200 binders were experimentally investigated. For comparison, parameters such as drop number, wet and dry compressive strength, preheated and fired compressive strength, and pellet porosity were measured. The results demonstrated that structural modification of organic binders in the form of VETA OB200 can provide desirable mechanical properties for wet, dry, and fired pellets.