Effects of solids feeder and riser exit configuration on establishing high density circulating fluidized beds

Abstract Influences of configurations of solids feeding device and riser exit on the flow behaviors of gas–solid in a solids circulation system were studied in order to investigate a highly dense solids circulation at high velocity. Experiments were carried out in a lab-scale circulating fluidized bed (0.05 m-ID × 4.5 m-H) cold model with FCC particles ( d p  = 70 μm, ρ s  = 1740 kg/m 3 ) as a bed material. Three kinds of solids feeders (Loop-seal, J-valve and L-valve type) and three different shapes of riser exits (C, L and T-shape) were employed. It was found that the solids mass flux ( G s ) increased with increasing the primary gas velocity ( U 1 ) in all configurations, and the level of G s with the L-valve was much higher than the other feeders and the high G s enabled solids holdup ( e s ) in the riser to be relatively dense at high U 1 . Among the three riser exit configurations investigated (C, L and T-shape), on the other hand, C-shape exit provided high G s and e s at high U 1 . In this study, a highly dense solids circulation was observed under conditions such as LV solids feeder and C-shape riser exit with sufficient solids inventory ( I s ). The effects of the inlet and exit configurations on the gas–solid flow behaviors from a dilute to a dense-phase were discussed based on correlation dimension ( D c ) and Kolmogorov entropy ( K ) obtained by chaos analysis of pressure fluctuations.

[1]  J Baeyens,et al.  Gas fluidized beds operating at high velocities: a critical review of occurring regimes , 2001 .

[2]  Jesse Zhu,et al.  Particle velocity and flow development in a long and high-flux circulating fluidized bed riser , 2001 .

[3]  Hsiaotao Bi,et al.  Suspension densities in a high-density circulating fluidized bed riser , 1999 .

[4]  Dawid Jakobus Duvenhage,et al.  Synthol reactor technology development , 2002 .

[5]  Sung Won Kim,et al.  Effects of particle properties on solids recycle in loop-seal of a circulating fluidized bed , 2002 .

[6]  Joachim Werther,et al.  Flow phenomena in the exit zone of a circulating fluidized bed , 2002 .

[7]  Shiqiu Gao,et al.  Necessary parameters for specifying the hydrodynamics of circulating fluidized bed risers—a review and reiteration , 2003 .

[8]  John R. Grace,et al.  Circulating fluidized beds , 1996 .

[9]  F. Scala,et al.  Fluidized bed combustion of alternative solid fuels , 2004 .

[10]  Ye-Mon Chen,et al.  Recent advances in FCC technology , 2006 .

[11]  János M. Beér,et al.  High efficiency electric power generation: The environmental role , 2007 .

[12]  S. Bhattacharya,et al.  Combination of thermochemical recuperative coal gasification cycle and fuel cell for power generation , 2005 .

[13]  Filip Johnsson,et al.  Characterization of fluidization regimes by time-series analysis of pressure fluctuations , 2000 .

[14]  Atsushi Tsutsumi,et al.  Nonlinear dynamics of gas-solid circulating fluidized-bed system , 2000 .

[15]  Jin Yong,et al.  Mass flux profiles in a high density circulating fluidized bed , 1997 .

[16]  Liang-Shih Fan,et al.  Behavior of the Dense-Phase Transportation Regime in a Circulating Fluidized Bed , 2006 .

[17]  L. Shadle,et al.  Impact of the Circulating Fluidized Bed Riser on the Performance of a Loopseal Nonmechanical Valve , 2007 .

[18]  John R. Grace,et al.  Characteristics of gas-fluidized beds in different flow regimes , 1999 .

[19]  A. Tsutsumi,et al.  Development of cobalt catalysts for the steam reforming of naphthalene as a model compound of tar derived from biomass gasification , 2005 .

[20]  Hsiaotao Bi,et al.  Flow regime diagrams for gas-solid fluidization and upward transport , 1995 .

[21]  Hermann Hofbauer,et al.  In-Bed Catalytic Tar Reduction in a Dual Fluidized Bed Biomass Steam Gasifier , 2004 .

[22]  E. Anthony.  Fluidized bed combustion of alternative solid fuels ; status, successes and problems of the technology , 1995 .

[23]  F. Berruti,et al.  An innovative non-mechanical solids feeder for high solids mass fluxes in circulating fluidized bed risers , 1996 .

[24]  S. D. Kim,et al.  EFFECTS OF SECONDARY AIR INJECTION ON GAS-SOLID FLOW BEHAVIOR IN CIRCULATING FLUIDIZED BEDS , 2000 .

[25]  Mohammad Asadullah,et al.  Syngas production by biomass gasification using Rh/CeO2/SiO2 catalysts and fluidized bed reactor , 2004 .

[26]  F. Takens.  Detecting strange attractors in turbulence , 1981 .

[27]  Hsiaotao Bi,et al.  Flow behavior and regime transition in a high-density circulating fluidized bed riser , 2004 .

[28]  Owen E. Potter,et al.  Circulating fluidized beds — diameter, solids hold-up, axial gas-mixing, and contact efficiency , 2000 .

[29]  J. X. Bouillard,et al.  Dimension measurements of hydrodynamic attractors in circulating fluidized beds , 1997 .

[30]  Daizo Kunii.  Chemical Reaction Engineering and Research and development of gas solid systems , 1980 .

[31]  Fei Wei,et al.  Inlet and outlet effects on flow patterns in gas-solid risers , 1998 .

[32]  Franco Berruti,et al.  Evaluation of the gas–solid suspension density in CFB risers with exit effects , 2000 .

[33]  D. Bai,et al.  Quantitative estimation of solids holdups at dense and dilute regions of circulating fluidized beds , 1999 .

[34]  John R. Grace,et al.  Reflections on turbulent fluidization and dense suspension upflow , 2000 .

[35]  Coal gasification characteristics in a downer reactor , 2001 .

[36]  Toshiyuki Suda,et al.  The Superior Technical Choice for Dual Fluidized Bed Gasification , 2006 .