Flow structure and thickness of annular downflow layer in a circulating fluidized bed riser

Kim, SW
Külah, Görkem
Bi, HT
Lim, CJ
Grace, JR
Flow structures were determined in a circulating fluidized bed (CFB) riser (0.203 m i.d. x 5.9 m high) of FCC particles (d(p)=70 mum, rho(s)= 1700 kg/m(3)). A momentum probe was used to measure radial momentum flux profiles at several levels and to distinguish between upward and downward flow regions. Time-mean dynamic pressure (DeltaP(m)) decreases towards the wall in the range U-g=5-8 m/s, G(s)=10-340 kg/m(2) s. The thickness of the annular downflow layer based on DeltaP(m)=0 reaches a maximum with increasing height. The annular downflow layer disappears locally with increasing solids mass flux (G(s)) at a constant gas velocity, with achievement of the dense suspension upflow (DSU) regime. A new correlation is developed to predict the time-mean thickness of solids down-flowing layer based on solids mass flux and momentum flux. It successfully accounts for the variation of the annular layer thickness with height and Gs, and covers a wide Gs range right up to near the onset of the DSU regime.


Flow behavior and regime transition in a high-density circulating fluidized bed riser
Kim, SW; Külah, Görkem; Bi, H; Lim, CJ; Grace, JR (2004-09-01)
Flow behavior and flow regime transitions were determined in a circulating fluidized bed riser (0.203 m i.d. x 5.9 m high) of FCC particles (d(p) = 70 pm, rho(p) = 1700 kg/m(3)). A momentum probe was used to measure radial profiles of solids momentum flux at several heights and to distinguish between local net upward and downward flow. In the experimental range covered (U-g = 5-8 m/s; G(s) = 22-345 kg/m(2) s), the fast fluidization flow regime was observed to coexist with dense suspension upflow (DSU). At a...
Multiscale analysis of solids flux signals measured in a high density circulating fluidized bed using wavelet transformation
Külah, Görkem (2005-05-13)
In order characterize the annulus thickness in a high density circulating fluidized bed, local instantaneous solids fluxes are measured using a three-fibre optical probe in a 0.20 m diameter, 5.9 m tall CFB riser operating at superficial gas velocity of 6 m/s and solids circulation flux of 330 kg/m(2)s, with FCC particles of mean diameter 70 mu m and density 1700 kg/m(3) as the bed material. Measurements obtained at three axial levels (z = 0.76, 1.27, 3.10 m) and six radial locations (r/R = 0.94, 0.88, 0.75...
Experimental investigation of fludized bed to be used as solar thermal energy storage
Polat, Esra; Tarı, İlker; Department of Mechanical Engineering (2019)
An air-granular particle fluidized bed system with dimensions of 0.08 m x 0.4 m x 0.08 m designed and analyzed experimentally and modeled with a commercial CFD software. The aim of the hydrodynamic and thermal experiments is validation of the numerical model previously developed by Serdar Hiçdurmaz. For this purpose, an experimental setup is built at METU and CFD model of Hiçdurmaz is modified for the new geometry with the same solution settings. First-order time discretization and Eulerian-Eulerian approac...
Hydrodynamics of Conical Spouted Beds With High Density Particles
Sari, Salih; Polat, Aylin; Zaglanmis, Dogukan; Külah, Görkem; Köksal, Murat (2008-05-01)
An extensive experimental investigation of conical spouted beds with high density particles were carried out by measuring bed pressure drop, particle velocity and solids hold-up in a 15 cm ID conical spouted bed at three different cone angles (30°, 45°, 60°) with Yttria-stabilized zirconia (YSZ) particles (ρp = 6050 kg/m3 ). The results show that the minimum external spouting velocity increases with cone angle, particle diameter and static bed height. The bed is characterized by two regions: upward moving p...
Flow structure characterization in conical spouted beds using pressure fluctuation signals
MOSTOUFI, Navid; Külah, Görkem; KÖKSAL, MURAT (2015-01-01)
Characteristics of the hydrodynamics of conical spouted beds were revealed by analyzing pressure fluctuation signals in the frequency domain. Experiments were carried out in spouted beds with three different cone angles (30 degrees, 45 degrees, 60 degrees) and high density spherical particles (rho(p) = 6050 kg/m(3)) with diameters of 0.5 or 1 mm. Different hydrodynamic structures in the movement of solids were identified by examining pressure fluctuations of the bed in the frequency domain. Peaks in the pow...
Citation Formats
S. Kim, G. Külah, H. Bi, C. Lim, and J. Grace, “Flow structure and thickness of annular downflow layer in a circulating fluidized bed riser,” POWDER TECHNOLOGY, pp. 48–58, 2004, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/42833.