Pelletising

Pelletising is a process of size enlargement where loose bulk materials are agglomerated into dense, uniformly shaped pellets. This transformation is typically achieved by combining fine particles with a binder and then shaping them in a rotating drum or a pan. The rotation causes the material to tumble and form spherical or near-spherical aggregates. The binder, which can be water, bentonite, cement, or specialized chemicals, acts as a glue, holding the particles together as the pellets are formed and dried.

The primary purpose of pelletising is to improve the handling and processing characteristics of fine-grained materials. Pellets are less prone to dusting, segregation, and compaction compared to their loose counterparts, making them easier to transport, store, and feed into processing equipment. This is particularly important in industries such as iron ore mining, where fine iron ore concentrate is converted into pellets for efficient use in blast furnaces and direct reduction plants. Other applications include the production of animal feed, fertilizers, and waste material solidification.

The process involves several stages. First, the raw material is mixed with the binder. Then, the mixture is fed into a pelletising machine, such as a disc pelletiser or a drum pelletiser. As the machine rotates, the material rolls, forming small nuclei that grow into larger pellets through a process of accretion. Finally, the green pellets, which are still soft, are typically dried to harden them and remove moisture. In some cases, firing or sintering may follow to further increase their strength and durability. The size and quality of the pellets can be controlled by adjusting factors like the speed of rotation, the angle of the machine, the amount of binder, and the moisture content.