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Item type:Publication, Access status: with files , Particle size segregation in bi and penta-disperse gas–solid fluidized beds: CFD-DEM and recurrence CFD simulationsWe studied the time evolution of segregating particle fractions in gas–solid fluidized beds by unresolved CFD-DEM and data-based recurrence CFD (rCFD). First and foremost, we incorporated segregating particle fractions into rCFD by superposing a fractional drift velocity to the velocity of the solid bulk material. From an algorithmic viewpoint, fractional drift was implemented by discrete face swaps. We tested this novel rCFD approach with different superficial gas velocities and different bi-disperse bed inventories. rCFD predictions agreed very well with corresponding full CFD-DEM results with respect to the time-evolution of fractional centre-of-gravity as well as spatial line profiles of fractional mean volume fraction. In order to explore the validity range of the underlying databases, we intentionally ran rCFD at deviating conditions. In a first test, we showed that rCFD simulations could indicate regime-changing de-fluidization even if de-fluidization itself was not pictured in the database. In a second test, we performed penta-disperse rCFD simulations based on an equivalent bi-disperse database. Hereby, we found out that rCFD predictions were only accurate if the penta-disperse bed inventory did not lead to changing overall bed dynamics. Finally, we proved the feasibility of rCFD simulations of a granulation process featuring local particle growth as well as continuous feed input and product output. In all cases, rCFD simulations ran more than four orders of magnitude faster than corresponding CFD-DEM simulations, eventually allowing for real-time simulations of spatially resolved particle segregation in fluidized beds.Publicationtype: Journal Article2 17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Control of segregation by non-uniform aeration in a fluidized bed spray granulator(Elsevier, 2024-02-15); ; Puttinger, StefanControlling and influencing the rate of particle growth in spray granulators is key for consistent product quality and size, while reducing energy consumption and product re-circulation. To this end, we have implemented a new control device to actively change the fluidization topology of fluidized spray granulators and to influence the local particle segregation in the areas affected by the granulation, selectively growing fine particle fractions at will. Simulations using computational fluid dynamics coupled with the discrete element method (CFD-DEM) demonstrate how the different operational modes can be switched in a short period of time, resulting in full local segregation in less than 40 s, without changing the fluidization air or inlet temperature. It is shown how a central spout preferentially drags big particles to the top of the bed, while a side aeration system, where two smaller spouts are opened at the outermost sides of the bed, creates a concentration of fines in the spraying region. This process can be repeated as long as the fluidization velocity of all particle sizes in the bed can be attained and full fluidization is underway. The spout regime could be used to clean the distributor plate of undesired big or overgrown particles, and side aeration to preferentially grow finer particles, while homogeneous aeration should be the default operation mode when no anomalies are detected.Publicationtype: Journal ArticleScopus© Citations 1 14 47