Flow properties and inter-particle forces in fuel powders

This work studied the mechanical properties of a series of industrial fuel powders: bituminite, lignite, and petroleum coke. Sieved cuts of these powders were assessed and the flow properties of each sample were used to calculate tensile strengths as functions of consolidation stress. In addition, BET surface areas and dispersive surface energies were estimated from surface energy analysis. To analyze the bulk flow properties of these fuel powders in terms of micro-contact mechanics, the fundamentals of fuel powder adhesion and consolidation were reconsidered based on the “stiff particles with soft contacts” model proposed by Tomas. In the present work, a multi-contact concept was introduced to account for the irregular shapes of actual particles. This modified model was based on elastic–plastic contact deformation theory and was employed to describe the contact between rough particles and to estimate the associated inter-particle forces. The results were used in conjunction with the Rumpf approach to relate the isostatic tensile strength to the degree of consolidation. Applying average values for the powder compressibility parameters allowed the model to be used for predictive purposes, and an acceptable level of agreement was found between predicted and measured tensile strengths.