pelletizing

Pelletizing is the process of forming fine materials into small, dense, uniformly sized pellets. It is used to improve handling, storage, transport, and combustion properties, and to convert materials that are prone to dusting or segregation into stable shapes. The exact method depends on material properties such as hardness, moisture, and plasticity, but common goals are to achieve a consistent particle size distribution and sufficient mechanical strength.

Common pelletizing technologies include extrusion-based pelletizing for plastics and some food products, in which material is melted or softened and forced through a die to create strands that are cut into pellets; disc or pan granulation and roller pelletization, which form agglomerates from powder or fines using rotation and sometimes binders; and agglomeration techniques used for biomass, feed, and fertilizers that compact material under pressure in a pellet mill or pelletizer.

Applications vary widely. Wood and agricultural residues are pelletized into fuel pellets; animal feed is produced by adding binders and sometimes nutrients; fertilizer pellets standardize nutrient distribution and reduce dust; in the metals industry, iron ore and other fines may be pelletized to improve permeability and reducibility in blast furnaces; plastics are pelletized to create feedstock for extrusion and molding.

Typical process steps include size reduction to uniform feed, moisture adjustment to an optimum level, addition of binders or conditioning agents if required, pellet formation, and cooling and drying prior to screening and packaging. Quality control monitors density, durability, fines content, moisture, and size distribution.

Pellet quality depends on particle properties, binder choice, equipment design, and operating conditions. Energy use and safety considerations are important, as is environmental management for binder emissions and dust.