Granulates

Granulates are discrete solid particles that constitute a broad category of granular materials. They are typically larger than powders but small enough to be handled as individual grains, with particle diameters commonly ranging from about 0.1 to 4 millimeters, though exact definitions vary by industry. Granulates can be natural, such as sand, salt, or grains, or manufactured, including sugar crystals, fertilizer pellets, plastic pellets, and pharmaceutical granules. They exhibit flow under gravity and package well, but their behavior depends on size distribution, shape, moisture, and surface texture, which influence bulk density, porosity, and angle of repose.

Granulation is the process used to convert powders or finer particles into granulates. Techniques include extrusion-spheronization, agglomeration by wet or dry methods, spray drying, and drum or pan granulation. The choice of method affects size uniformity, density, strength, and disintegration properties, which are important for handling and downstream processing.

Properties and testing: key indicators include particle size distribution, bulk density, tap density, compressibility, moisture content, and flowability. Common measurement methods are sieve analysis, laser diffraction, dynamic image analysis, and standard flow tests. Granulates are designed to balance stability during storage with reactivity or dissolution when used in formulations.

Applications: in construction, granulates serve as aggregates and fill material; in agriculture, pelleted or granulated fertilizers control release rates; in the food industry, instant products and crystalline sweeteners use granulates; in pharmaceuticals, granulated excipients and controlled-release granules are standard. Environmental and safety considerations include dust generation, respiratory hazard, and the potential for dust explosions with combustible powders.