Use of boron compounds as binders in iron ore pelletization

Low grade iron ores with impurity gangue minerals containing silica and alumina must be upgraded to an acceptable level of iron content. Concentrates, due to their fine sizes, are not suitable to be directly charged to the iron-making processes such as the blast furnace or the DR-plant. Hence, an agglomeration technique should be applied to fine concentrate. The most commonly employed one is pelletizing in iron ore industry. In pelletizing, iron ore, water and a binder are balled in a mechanical disc or drum to produce agglomerates. Bentonite is the most widely used binder. However, it is considered as an impurity due to its high SiO2 and Al2O3 content. Many researchers have investigated different binders, mostly of organic origin, in pursuit of finding a viable alternative binder to bentonite. Organic binders were found to yield good quality green and dry pellets. However, they fail to impart enough strength to the pre-heated and fired pellets as a result of insufficient slag bonding. Boron compounds free of silica and alumina are thought to be a potential solution to overcome the lack of slag forming constituents encountered with organic binders as they are known for their low melting temperatures as well as for their ability to also lower the melting temperatures of silicates. A few researchers have investigated the use of boron compounds in iron ore agglomeration and found promising results which have been covered in this paper