Mass transfer between bubbles and the dense phase in gas fluidized beds

Mass transfer between a bubble and the dense phase in gas fluidized beds of Group A and Group B particles was proposed based on previous experimental results and literature data. The mass transfer coefficient between bubbles and the dense phase was determined by k(be) = 0.21d(b). A theoretical analysis of the mass transfer coefficient between a bubble and the dense phase using diffusion equations showed that the mass transfer coefficient between a bubble and the dense phase is k(be) proportional to epsilon(mf)root Du(b)/d(b) in both three- and two-dimensional fluidized beds. An effective diffusion coefficient in gas fluidized beds was introduced and correlated with bubble size as De = 13.3d(b)(2.7) for Group A and Group B particles. The mass transfer coefficient kbe can then be expressed as k(be) = 0.492 epsilon(mf)root u(b)d(b)(1.7) for bubbles in a three-dimensional bed and k(be) = 0.576 epsilon(mf)root u(b)d(b)(1.7) for bubbles in a two-dimensional bed. (C) 2014 Published by Elsevier B.V. on behalf of Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences.