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Title: Study of defluidization behaviour of industrial reactive particles
Author: Macri, Domenico
ISNI:       0000 0004 7659 9355
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2018
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The overall objective of this research is to assess the effect of high temperature on the flow properties and fluidization behaviour of mixtures of petroleum coke and different titanium ores. To this end, a twofold approach based on fundamental fluidization and rheological measurements was followed with the aim of evaluating how the particle-particle interactions change with temperature. On the one hand, the fluidization behaviour of every single component of the mixture and of the mixture itself have been studied at process temperatures ranging from ambient up to 500 °C in a specially designed heated fluid-bed reactor. Experiments were carried out under different fluidization conditions, where the carbon combustion causes defluidization, varying the amount of coke and its size distribution present in the bed. The latter is particularly important as coke particles are prone to promote ores particles' sintering and thus leading to poor mixing and segregation. Fundamental fluidization tests were performed using the unique X-ray Imaging technique available at UCL, which enabled to visualise the internal flow pattern inside the reactor and to obtain quantitative information on voidage distribution, bed expansion, mixing and segregation within the fluidized bed. Simultaneous measurements of local temperatures and pressure drop across the bed were carried out in order to detect possible aggregation and sintering phenomena. The tests showed that combination of operative conditions and coke characteristics have a significant role on the formation of the aggregates and on their properties. The resulting lumps of aggregated particles were collected and systematically characterized by performing specific analysis aimed at investigating their mechanical properties and the chemical compositions of the sintered bonds formed. On the other hand, the unique heated annular shear cell available at the University of Salerno has been used to assess the changes of the bulk flow properties of the different types of titanium ores at ambient and with increasing temperature. These experiments highlighted a significant increase with temperature of the macroscopic bulk flow properties, such as unconfined yield strength and cohesion, which resulted in a lower flowability of the samples. In parallel, two different models were used to correlate the experimental results with the microscopic interparticle interaction forces. Such outcomes provided an indication of the ability of the powders to flow and underpinned the link between the fluidization and the rheological behaviour below the minimum fluidization conditions: the capability of the powders to fail under a certain load was directly correlated to their capability to attain fluidization.
Supervisor: Lettieri, P. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available