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Item type:Publication, Access status: without files , Real-time magnetic resonance imaging of fluidized beds with internalsThe effect of internals on the fluidization dynamics in three-dimensional (3D) cylindrical fluidized beds was studied using real-time magnetic resonance imaging. Instantaneous snapshots of particle velocity and particle position were acquired for gas velocities U below and above the minimum fluidization velocity Umf. Below Umf, we found local fluidization and gas bubbling in areas adjacent to an inserted horizontal tube, likely caused by the gas locally exceeding Umf as it flows around the insert. Above Umf, the presence of the insert in the bed affected the fluidization dynamics. The wake region above the insert exhibited a lower average particle velocity and reduced velocity fluctuations as well as a substantially reduced number and size of gas bubbles as compared to a reference bed without internals. The extent of this wake region was found to be approximately as wide as the insert, and it extended from the top of the insert to the free surface of the bed. Moreover, the presence of internals also affected the regions below the insert by showing an increased rate of bubble formation directly below the inserted tube. The present work can provide relevant information on the design of fluidized beds with internals. Moreover, the data gathered in this work can be used to validate the accuracy of 3D numerical models of gas-solid systems.Publicationtype: Journal Article39 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Fluidized Beds with Internals: A Real-Time Magnetic Resonance Imaging Study of Gas Bubbles and Particle MotionFluidized beds are frequently equipped with internals in order to modify the fluidization dynamics within the bed, such as reducing the size of gas bubbles, or enforcing specific particle circulation patterns[1,2]. Traditionally, the design of internals is often based on rules of thumb and empirical correlations derived from optical measurements in pseudo two-dimensional (2D) systems, or by inserting probes into 3D systems. However, such measurements are either influenced by wall effects (pseudo 2D systems) or do interfere with the particle flow (intrusive probe measurements). More recently, sophisticated tomographic techniques have been applied to study fluidization dynamics in freely bubbling fluidized beds, such as X-ray tomography[3], electrical capacitance tomography[4] and magnetic resonance imaging (MRI)[5–7]. In order to design and scale-up fluidized bed reactors with internals reliably and efficiently, we need fundamental insight into fluidization dynamics in large, 3D systems with internals.Publicationtype: Conference Paper50