The undesirable agglomeration and hardening (caking) of hygroscopic particulate solids such as fertilizers, salts, sugars, powdered food products, and pharmaceutical powders pose a significant challenge across various scales of industrial operations, hindering production efficiency. Caking is especially critical in silo storage, potentially leading to high dynamic loads and catastrophic failures when large agglomerated structures like arches or ratholes collapse. Our novel approach to address this problem leverages our extensive experience in analyzing and testing caking across diverse materials and conditions and integrates computational fluid dynamics (CFD) modeling to simulate coupled heat transfer and moisture transport within porous media. The CFD model predicts temperature-induced moisture migration in a silo under diverse environmental conditions to provide insights into critical moisture accumulation zones within silos. This informs the selection of high-risk environmental parameters (temperature, relative humidity, and initial water activity) for targeted static and dynamic caking tests. Jenike shear tests cells1 incorporating pre-consolidation and controlled environmental chamber experiments are employed to quantify the impact of temperature, relative humidity, and storage time on caking intensity in terms of unconfined yield strength. Coupling this with the dynamic vapor sorption analysis defines the safe storage (non-caking) water activity as a function of temperature and allows the CFD to predict critical environmental conditions for caking initiation in storage. The fundamental understanding of caking phenomena provided by our integrated approach enables the investigation of practical mitigation strategies, such as bin insulation to minimize temperature gradients and aeration to control moisture levels, directly translating to ensured product quality and enhanced safety and handling efficiency across diverse industrial applications.
