Non-invasive investigation of the cross-sectional solids distribution in CFB risers by X-ray computed tomography

Hensler, Timo; Firsching, Markus; Bonilla, Juan Sebastián Gómez; Wörlein, Thorsten; Uhlmann, Norman; Wirth, Karl‐Ernst

doi:10.1016/j.powtec.2016.04.030

Cited by 16 publications

(3 citation statements)

References 23 publications

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“…They reported an increase in solid circulation rate with liquid velocity and solid feed pipe diameter, but a decrease in solid circulation rate with increasing particle density and size. Roy et al [25], and Hensler et al [26] used a radioactive technique to determine the solid circulation rate. The basic theory was to estimate the volumetric flowrate of particles by measuring the particles velocity and volume fraction in the downcomer.…”

Section: Introductionmentioning

confidence: 99%

Solid Circulating Velocity Measurement in a Liquid–Solid Micro-Circulating Fluidised Bed

2020

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Liquid–solid circulating fluidised beds (CFB) possess many qualities which makes them useful for industrial operations where particle–liquid contact is vital, e.g., improved heat transfer performance, and consequent uniform temperature, limited back mixing, exceptional solid–liquid contact. Despite this, circulating fluidised beds have seen no application in the micro-technology context. Liquid–solid micro circulating fluidised bed (µCFBs), which basically involves micro-particles fluidisation in fluidised beds within the bed of cross-section or inner diameter at the millimetre scale, could find potential applications in the area of micro-process and microfluidics technology. From an engineering standpoint, it is vital to know the solid circulating velocity, since that dictates the bed capability and operability as processing equipment. Albeit there are several studies on solid circulating velocity measurement in CFBs, this article is introducing the first experimental study on solid circulating velocity measurement in a CFB at micro-scale. The experimental studies were done in a novel micro-CFB which was fabricated by micro milling machining 1 mm2 cross-section channels in Perspex and in a 4 mm2 cross-section micro-CFB made by additive manufacturing technology. Soda-lime glass and polymethyl methacrylate (PMMA) micro-particles were employed as solid materials and tap water as the liquid medium. The digital particle image velocimetry (PIV) method was used as a measurement technique to determine the particle velocity in the micro-CFB system and validated by the valve accumulation technique using a novel magnetic micro-valve. The measured critical transition velocity, Ucr, is comparable to the particle terminal velocity, i.e., the normalised transition velocity is approximately 1 in line with macroscopic systems results and our previous study using simple visual observation. As in macroscopic CFB systems, Ucr decreased with solid inventory (1–9%) and finally becomes stable when the solid inventory is high enough (10–25%) and it increases with a reduction in particle size and density.

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Section: Introductionmentioning

confidence: 99%

Solid Circulating Velocity Measurement in a Liquid–Solid Micro-Circulating Fluidised Bed

2020

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“…Die Verwendung der Computertomographie als Messverfahren ist bei vielen technischen Untersuchungen mittlerweile etabliert. Beispielweise wird die CT für die Bestimmung der Feststoffdichteverteilung in einem Riser , der Strukturaufklärung in Biomasse Festbetten oder der hydrodynamischen Untersuchung von porösen Schwammstrukturen genutzt . Laiblin et al haben als weiteres nicht‐invasives und überlagerungsfreies Messverfahren bei der Betrachtung von chromatographischen Säulen Magnetresonanztomographie verwendet.…”

Section: Introductionunclassified

Measurement of Fluid Dynamics in Random Packings Using High‐Resolution Computed Tomography

Schug

Arlt

2016

Chemie Ingenieur Technik

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Durch Aufnahme computertomographischer Bilder über die Höhe einer Füllkörperkolonne sind lokale und integrale Werte für den Holdup, die benetzte Füllkörperoberfläche und die Stoffaustauschfläche bestimmt worden. Hierfür sind der Raschig Super‐Ring, RMSR und Raflux‐Ring über einen weiten Betriebsbereich untersucht worden. Die Ergebnisse zeigen große Unterschiede zwischen den drei Füllkörpertypen und lassen sich aufgrund der hohen räumlichen Auflösung der Messtechnik quantifizieren. Die Resultate der integralen Werte sind weitgehend unabhängig von der Füllkörperschüttung und auch nach Neuschüttung der Füllkörper reproduzierbar.

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“…In addition, the total time-mean values are symmetrical. It can be concluded that the rotational symmetry of the core-annular structure reported in the experimental research should be in the sense of time average [32]. The symmetry of the time-averaged distribution indicates good particle Figure 9 gives the radial porosity distribution at the section with a height of 0.015125 m for slugging cases 1 and 2.…”

Section: Core-annular Structurementioning

confidence: 72%

CFD-DEM Simulation of Slugging and Non-Slugging Fast Fluidization of Fine Particles in a Micro Riser

Wu,

2023

Processes

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The discrete element method (DEM) coupled with computational dynamics (CFD) has been considered one of the most sensitive ways of studying the micro fluidized bed. This article proposes a so-called particle circumstance-dependent drag model that is dependent on a particle’s complex circumstances. Slugging and non-slugging fast fluidization in a micro fluidized bed is modeled with the use of the CFD-DEM. The results show that the formation and the fragmentation of clusters in a slugging fast fluidized state are clearly captured, and both have time synchronization. However, with the increase in gas velocity, the boundary of the dense and dilute phases turns blurry and the slugs disappear. Furthermore, there exists a relatively serious backmixing of particles in the slugging fast fluidization, while the backmixing effect weakens in the non-slugging fast fluidization. Moreover, the outlet solid flux decreases compared with those in the big fluidized beds for the slugging fast fluidized bed due to the micro size effect, while the micro size effect on the solid flux is not distinct for the non-slugging fast fluidized bed. Last but not least, the radial porosity with slugging exhibits a weakened core-annulus structure compared with the correlated radial porosity in the big fluidized beds. The radial porosity without slugging tends to approach the correlated core-annulus structure.

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Non-invasive investigation of the cross-sectional solids distribution in CFB risers by X-ray computed tomography

Cited by 16 publications

References 23 publications

Solid Circulating Velocity Measurement in a Liquid–Solid Micro-Circulating Fluidised Bed

Solid Circulating Velocity Measurement in a Liquid–Solid Micro-Circulating Fluidised Bed

Measurement of Fluid Dynamics in Random Packings Using High‐Resolution Computed Tomography

CFD-DEM Simulation of Slugging and Non-Slugging Fast Fluidization of Fine Particles in a Micro Riser

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