Particle Size Enlargement

Size enlargement concerns those processes that bring together fine powder particles into larger masses to improve the properties of the powders. Many diverse industries benefit from size enlargement processes. Examples discussed herein include fertilizer granulation, iron ore pelletization, tablet feeds for pharmaceuticals, instant food products, and the processing of mineral and chemical products. This article primarily considers those processes in which the creation of coarse granular material from fines is the objective. The characteristics of individual agglomerates are important only in their effect on the properties of the bulk granular product. Following an initial discussion of particle-bonding mechanisms and the theory and measurement of agglomerate strength, size enlargement processes and equipment, including principal design parameters, are described. These processes are considered on the basis of the principal mechanism used to bring the particles together into agglomerates. The categories used are agglomeration by tumbling and other agitation methods, pressure compaction and extrusion methods, heat reaction, fusion, and drying methods, and agglomeration from liquid suspensions by competitive wetting. Keywords: agglomeration; granulation; pelletizing; powder processing; particle technology