Computation and measurements of mass transfer and dispersion coefficients in fluidized beds

Abstract Conventional design of circulating fluidized beds requires the knowledge of dispersion and mass transfer coefficients, expressed in dimensionless forms as Sherwood numbers. However, these are known to vary by five or more orders of magnitude. Furthermore, the Sherwood numbers for fine particles reported in the literature are several orders of magnitude lower than the Sherwood number of two for diffusion to a single particle. We have shown that by replacing the particle diameter in the conventional Sherwood number with cluster or bubble diameter, the modified Sherwood number is again of the order of two. We have also shown that the kinetic theory based computational fluid dynamics codes correctly compute the dispersion and mass transfer coefficients. Hence, the kinetic theory based computational fluid dynamics codes can be used for fluidized bed reactor design without any such inputs.

[1]  Ronald W. Breault,et al.  Computation of gas and solid dispersion coefficients in turbulent risers and bubbling beds , 2007 .

[2]  William J. Koves,et al.  Kinetic theory based CFD simulation of turbulent fluidization of FCC particles in a riser , 2006 .

[3]  Wei Ge,et al.  Simulation of Heterogeneous Structure in a Circulating Fluidized-Bed Riser by Combining the Two-Fluid Model with the EMMS Approach , 2004 .

[4]  Dimitri Gidaspow,et al.  Dispersion and Mass Transfer Coefficients in Fluidized Beds , 2012 .

[5]  J. Werther,et al.  Radial gas mixing in the upper dilute core of a circulating fluidized bed , 1992 .

[6]  Dimitri Gidaspow,et al.  Hydrodynamics of fluidization using kinetic theory: an emerging paradigm: 2002 Flour-Daniel lecture , 2004 .

[7]  M. Streat,et al.  Mass transfer in fixed and fluidized beds , 1985 .

[8]  Dimitri Gidaspow,et al.  Effect of electric field on the hydrodynamics of fluidized nanoparticles , 2008 .

[9]  F. Wei,et al.  Lateral and Axial Mixing of the Dispersed Particles in CFB , 1995 .

[11]  R. Jackson,et al.  Frictional–collisional constitutive relations for granular materials, with application to plane shearing , 1987, Journal of Fluid Mechanics.

[12]  Won Namkung,et al.  Gas backmixing in a circulating fluidized bed , 1998 .

[13]  J. Werther,et al.  Gas-solids mixing and flow structure modeling of the upper dilute zone of a circulating fluidized bed , 1995 .

[14]  Andrew N. Norris,et al.  Particle granular temperature in gas fluidized beds , 1996 .

[15]  Wave propagation and granular temperature in fluidized beds of nanoparticles , 2007 .

[16]  William Polashenski,et al.  Normal solid stress in fluidized beds , 1997 .

[17]  Owen E. Potter,et al.  Circulating fluidized bed as a catalytic reactor: Experimental study , 1995 .

[18]  S. Oyama,et al.  Gas phase ozone decomposition catalysts , 1997 .

[19]  Pornpote Piumsomboon,et al.  Kinetic theory based computation of PSRI riser: Part II—Computation of mass transfer coefficient with chemical reaction , 2009 .

[20]  Liang-Shih Fan,et al.  Gas and solids mixing in a turbulent fluidized bed , 2002 .

[21]  Joseph Yerushalmi,et al.  Solids mixing in an expanded top fluid bed , 1985 .

[22]  Jinghai Li,et al.  An experimental comparison of gas backmixing in fluidized beds across the regime spectrum , 1989 .

[23]  Dimitri Gidaspow,et al.  Computational techniques: the multiphase CFD approach to fluidization and green energy technologies , 2010 .

[24]  W. J. Thiel,et al.  The mixing of solids in slugging gas fluidized beds , 1978 .

[25]  R. Dry,et al.  Gas residence-time characteristics in a high-velocity circulating fluidised bed of FCC catalyst , 1989 .

[26]  Velocity fluctuation interpretation in the near wall region of a dense riser , 2008 .

[27]  M. J. Rhodes,et al.  Gas mixing in gas-solids risers , 1993 .

[28]  Wei Ge,et al.  CFD simulation of concurrent-up gas-solid flow in circulating fluidized beds with structure-dependent drag coefficient , 2003 .

[29]  Ronald W. Breault,et al.  A review of gas–solid dispersion and mass transfer coefficient correlations in circulating fluidized beds , 2006 .

[30]  Owen E. Potter,et al.  Experimental investigation of models for fluidized bed catalytic reactors , 1976 .

[31]  Ronald W. Breault,et al.  Mass transfer in the core-annular and fast fluidization flow regimes of a CFB , 2009 .

[32]  Dimitri Gidaspow,et al.  Collisional viscosity of FCC particles in a CFB , 1996 .

[33]  O. E. Potter,et al.  Ozone decomposition in a 0.254 m diameter circulating fluidized bed reactor , 1993 .

[34]  William Polashenski,et al.  Measurement of particle phase stresses in fast fluidized beds , 1999 .

[35]  Yong Jin,et al.  Profiles of particle velocity and solids fraction in a high-density riser , 1998 .

[36]  D. Gidaspow.  Multiphase Flow and Fluidization: Continuum and Kinetic Theory Descriptions , 1994 .

[37]  Filip Johnsson,et al.  Gas mixing in circulating fluidised-bed risers , 2000 .

[38]  James Wei,et al.  A model for moving‐bed coal gasification reactors , 1978 .

[39]  Gas backmixing in the dense region of a circulating fluidized bed , 1999 .

[40]  M. Syamlal,et al.  Fluid dynamic simulation of O3 decomposition in a bubbling fluidized bed , 2003 .

[41]  Hsiaotao Bi,et al.  Baffle effects on performance of catalytic circulating fluidized bed reactor , 1991 .

[42]  F. Johnsson,et al.  Characteristics of gas mixing in a circulating fluidised bed , 2002 .

[43]  Ronald W. Breault,et al.  Computation of turbulence and dispersion of cork in the NETL riser , 2008 .

[44]  Wenli Song,et al.  Evaluation of downer reactor performance by catalytic ozone decomposition , 2008 .

[45]  C. S. Campbell,et al.  Particle pressures in gas-fluidized beds , 1991 .

[46]  F. Wei,et al.  Axial and lateral dispersion of fine particles in a binary-solid riser , 1998 .

[47]  D. Gidaspow,et al.  Explosive dissemination and flow of nanoparticles , 2006 .

[48]  Pornpote Piumsomboon,et al.  Kinetic theory based computation of PSRI riser: Part I—Estimate of mass transfer coefficient , 2009 .

[49]  P. Gayán,et al.  Radial gas mixing in a fast fluidized bed , 1997 .

[50]  Dimitri Gidaspow,et al.  Measurement of granular temperature and stresses in risers , 2004 .

[51]  Yiping Fan,et al.  CFD modeling and validation of the turbulent fluidized bed of FCC particles , 2009 .