Nouria Fatah

The shearing force provided by rotation blades induces a uniform coating layer of Co₃O₄ onto Al₂O₃ as Fischer–Tropsch solid catalysts.

Cement powder particles of micronic size tend to form agglomerates due to the influence of interparticle forces (Van der Waals forces). The formation of agglomerates results in an increased air-void in the solid structure (aerated powder) requiring an increase in water demand to sustain the feasibility of the structure. Consequently, if the compound formed is not stabilized, it would have low mechanical strength that may result in cracking of hardened cement. In this study, the results of cement powder consolidation and its flow properties show that its behaviour is controlled by internal forces (Van der Waals) and external forces (elastic and plastic). These forces have a direct influence on the powder structure, leading to a variable packing behaviour (void reduction). Consolidated cement powder shows a decrease in the void structure leading to a more efficient material. This study intends to determine the impact of interaction forces between cement particles during consolidation.

Abstract:  Many food recipes entail several homogenization steps for solid particles in hot or cold viscous liquids, such as pureed fruit and sugar, jam or sauce with mushroom pieces. Unfortunately, these unavoidable processes induce damage to the solid particles. To date, little is known of the extent and nature of the damage caused. Consequently, few clear guidelines are available for monitoring solid particle integrity when mixing solid/liquid suspensions in an agitated tank. In this study, an attempt is made to quantify the impact of various physical parameters including the influence of the rotational speed of the impeller and the processing time on particle attrition, when a suspension of large visco‐elastic particles in a highly viscous fluid is mixed under isothermal condition. Pectin gel particles were immerged in a viscous liquid and homogenized for various times and rotational speeds, while the evolution of the particle's morphological parameters was monitored. Then, a set of dimensionless numbers governing the attrition mechanism is established and some empirical process relationships are proposed to correlate these numbers to the morphological characteristics and mass balance ratios. From the conditions observed, it is clear that 2 dimensionless ratios could be responsible for a change in the damaging mechanisms. These 2 ratios are the Froude and impeller rotation numbers. Finally, in the conditions tested, mass balance ratios appear to be mainly sensitive to the impeller rotational number, while the shape ratios are both impacted by the Froude and impeller rotational numbers. Practical Application:  Damage to solid particles suspended in a stirred vessel reduce the final product quality in industrial cooking processes. Examples of this are fruit in jam or sauces with mushroom pieces. The attrition phenomenon was measured and the influences of the impeller rotational speed and processing time were evaluated quantitatively in function of dimensionless numbers. This study contributes key elements for the monitoring of damage to solids with a view to retaining solid integrity.