Study of bubble dynamics in gas-solid fluidized beds using ultrashort echo time (UTE) magnetic resonance imaging (MRI)

Abstract

Ultrashort echo time (UTE) imaging is commonly used in medical MRI to image 'solid' types of tissue; to date it has not been widely used in engineering or materials science, in part due to the relatively long imaging times required. Here we show how the acquisition time for UTE can be reduced to enable a preliminary study of a fluidized bed, a type of reactor commonly used throughout industry containing short T2 * material and requiring fast imaging. We demonstrate UTE imaging of particles with a T2 * of only 185 μs, and an image acquisition time of only 25 ms. The images are obtained using compressed sensing (CS) and by exploiting the Hermitian symmetry of k-space, to increase the resolution beyond that predicted by the Nyquist theorem. The technique is demonstrated by obtaining one-and twodimensional images of bubbles rising in a model fluidized bed reactor.

Magnetic resonance imaging of gas–solid fluidization with liquid bridging

“…Previous studies have been limited to device‐scale measurements, such as pressure oscillations and fluidization curves, measurements on pseudo‐2D fluidized beds using optical imaging and tomographic measurements on 3D beds of tracer particles, which are unable to capture behavior across the entire device on a temporally resolved level. In recent years, magnetic resonance imaging (MRI) has been able to generate detailed maps of both particle and gas motion in fluidized beds. A recent study using a medical MRI scanner and multichannel signal detection has enabled millisecond‐scale temporal resolution of maps of particle concentration and velocity in 3D beds with a diameter and height of over 100 particle diameters.…”

Machine Learning Assisted Characterization of Local Bubble Properties and Its Coupling with the EMMS Bubbling Drag

“…Bubble characteristics can be quantified by photographing/imaging technologies − or analyzing signals from intrusive probes , and nonintrusive pressure transducers . Combining high speed video photography with digital image analysis can enable the measurement of bubble distribution in two-dimensional reactors. − Adopting a threshold determined by either empiricism ,, or the Otsu algorithm, the bubbles can be distinguished from the emulsion phase based on solids concentration distribution, so their properties can be further obtained by using the mathematical morphology algorithm and the connected component labeling algorithm.…”

Selective oil‐phase rheo‐MRI velocity profiles to monitor heterogeneous flow behavior of oil/water food emulsions

“…In the past years, MRI has proven to be a suitable technique for the characterization of multiphase flows, such as high‐voidage bubbly flow, high‐speed gas flows, fluidized beds, liquid–liquid systems, and oil–water multiphase flow . More in particular, MRI velocimetry experiments performed on samples under deformation (commonly known as rheo‐MRI) have been successfully applied to the characterization of diluted and dense emulsions, identification of non‐local effects, sedimentation, and shear‐induced migration of droplets .…”