(231c) Formation and Growth of Crystal Bridges in Bulk Solids

During transport or storage of bulk products storage and environmental conditions effect on the handling properties of these bulk products produced by chemical, pharmaceutical and food industry. In consequence the bulk solids form lumps or solidify completely. These phenomena are known as caking. For further use of these caked products de-agglomeration is necessary. This process requires time and manpower. To minimize these costs the caking mechanism has to be identified in order to avoid conditions leading towards caking.

This work focuses on the caking behavior of a double particle system. For research on the caking behavior, the application of real storage conditions is very important. The effect of fife parameters on the particles during storage has been examined: moisture, temperature, pressure, particle size and storage time. Using an experimental setup, two particles of a specified size can be stored using different sets of parameters. The change of the geometry of the contact region between these two particles was analyzed using a Laser Scanning Microscope. After caking these two particles were pulled apart and the maximum force needed to destroy the bridge was measured.

With the experimental data a state of matter diagram for urea was determined. Further on, with the experimental results of the contact geometry and material properties like sorption isotherm, a physically based model was developed. This model describes the formation of a solid bridge between two particles for different sets of parameter. (The model was successfully validated, using bulk experiments) In a further step the transferability of the model to other substances was successfully tested using two different types of fertilizers